Stone Matrix Asphalt (SMA) for Airfield Pavements 2010 FAA Worldwide Airport Technology Transfer Conference Brian Prowell Don Watson Graham Hurley Ray Brown

Acknowledgements This work was conducted as part of the Airfield Asphalt Pavement Technology Program Project 04-04, Evaluation of Stone Matrix Asphalt for Airfield Pavements.This work was conducted as part of the Airfield Asphalt Pavement Technology Program Project 04-04, Evaluation of Stone Matrix Asphalt for Airfield Pavements.

Background SMA designed in Germany in the 1960’s as mix resistant to studded tiresSMA designed in Germany in the 1960’s as mix resistant to studded tires Adopted in US in 1991Adopted in US in 1991

Gradation

Aggregate Skeleton Stone Matrix Asphalt Mix

Aggregate Skeleton Dense-Graded Mix

9.5 mm NMAS SMA Surface Texture

How is SMA Different? GradationGradation Asphalt ContentAsphalt Content Dust ContentDust Content Stabilizing AdditivesStabilizing Additives

Marshall- 50 blow design has been used Marshall- 50 blow design has been used Improved performance over HMA Improved performance over HMA SMA Performance in the USA

Objectives of AAPTP Study The objectives: Evaluate performance of SMA pavementsEvaluate performance of SMA pavements develop technical guidance for the FAA to implement SMA on U.S. airfieldsdevelop technical guidance for the FAA to implement SMA on U.S. airfields

Documented SMA Use on Airfields AustraliaAustralia ChinaChina EuropeEurope BelgiumBelgium GermanyGermany ItalyItaly NorwayNorway United StatesUnited States

Experimental Design

Mix Combinations Coarse Aggregate Binder Grade P Blow SMA 50- Blow SMA 50 Gyrations SMA 65 Gyrations SMA 80 Gyrations SMA 100 Gyrations Diabase76-22XXXXXX Granite76-22XXXXXX Gravel76-22XXXXXX Limestone76-22XXXXXX Limestone64-22XXX Granite76-22XXXXXX

Rutting Susceptibility Laboratory evaluations typically show SMA to have increased rutting susceptibility compared to HMALaboratory evaluations typically show SMA to have increased rutting susceptibility compared to HMA Experiments to compare SMA and P401Experiments to compare SMA and P401 Three tests: stability and flow, repeated-load creep, and Hamburg wheel-trackingThree tests: stability and flow, repeated-load creep, and Hamburg wheel-tracking

Stability and Flow Aggregate High PG SMAP401 4% Air Voids3.5% Air Voids AC% Stability lbs Flow 0.01 inAC% Stability lbs Flow 0.01 in Diabase767.5NA 5.14,84611 Granite , ,19013 Granite , ,72011 Gravel767.61, ,79911 Limestone766.91, ,94012 Granite 164NA 5.34,20011 Limestone64 NA 5.53,1118 Average767.01, ,49912 Average64NA 5.43,65610

Repeated Load Permanent Deformation to Asses Rutting Potential 100 mm diameter, 150 mm height100 mm diameter, 150 mm height 6% air voids6% air voids 58  C (climatic high temp. - 6  C )58  C (climatic high temp. - 6  C ) 20 psi confinement20 psi confinement 0.1 second load; 0.9 second rest0.1 second load; 0.9 second rest 100, 200, 350 psi vertical load100, 200, 350 psi vertical load Continue for 10,000 cycles or until tertiary flowContinue for 10,000 cycles or until tertiary flow

With the repeated load test the permanent deformation performance of SMA mixtures and P401 mixtures were not significantly different.

Hamburg Test Test combines rutting performance with moisture susceptibility Uses a steel wheel 47 mm wide by 204 mm diameterUses a steel wheel 47 mm wide by 204 mm diameter Load = 685 N (154 lb)Load = 685 N (154 lb) Full test is 20,000 cyclesFull test is 20,000 cycles Temperature - 50  CTemperature - 50  C VTM %VTM % Tested under waterTested under water

With Hamburg, rutting very similar for P-401 and SMA

Overlay Tester Results

Fuel Resistance China has reported that SMA improves fuel resistanceChina has reported that SMA improves fuel resistance AAPTP evaluating fuel resistant sealers and bindersAAPTP evaluating fuel resistant sealers and binders Citgo Fuel Resistance TestCitgo Fuel Resistance Test –Soaked in kerosene for 24 hours –Mass loss less than 5% good

Fuel Resistance AggregateMixMass Loss, % Granite P SMA4.5 Gravel P SMA6.6

Deicer Resistance Immersion Tensile Test

Two Case Studies Aviano AFB, ItalyAviano AFB, Italy Spangdahlem AFB, GermanySpangdahlem AFB, Germany

Aviano SMA Constructed in 1999Constructed in 1999 Provided good performance up through 2010Provided good performance up through 2010 Some water issuesSome water issues More rubber build upMore rubber build up No groovingNo grooving

Rubber Build Up on SMA Aviano Air Force Base 2000

Aviano Surface Texture in 2000

Seepage of Water from Underneath, Aviano 2000

Draindown, Aviano 2000

Aviano, 2006

Aviano 2008

SMA Aviano Provided good performance to dateProvided good performance to date Good frictionGood friction Some water issuesSome water issues No groovesNo grooves

Based on good performance at Aviano, SMA was used at Spangdahlem in 2007

Spangdahlem AFB Milled and overlaid with SMA in 2007Milled and overlaid with SMA in 2007 High density obtainedHigh density obtained Some water vapor (blisters) problemsSome water vapor (blisters) problems

Spangdahlem 2006, patch

Spangdahlem 2006, cracking and condition of grooves

After mixture was milled, approximately 2 weeks of rainfall occurred causing the asphalt mixture to become soaked with moisture

Construction in 2007 The contractor used two asphalt plants, two pavers, and up to 8 rollersThe contractor used two asphalt plants, two pavers, and up to 8 rollers In place air voids were typically 3 to 4 percentIn place air voids were typically 3 to 4 percent

Spangdahlem, 2007, moisture on surface of SMA

Spangdahlem, 2007, blisters caused by water vapor

Plans are underway to remove and replace the SMA at Spangdahlem

Summary of SMA / P401 Comparison PropertyPerformance worse than P401 Performance similar to P401 Performance better than P401 Permanent Deformation X1X1 X2X2 Moisture Damage X Cracking X Fuel Resistance X Deicer Resistance X Texture X2X2 1 Based on laboratory tests performed as part of this study. 2 Based on review of the literature or in-service performance.

Recommendations SMA could cost 82 to 94 percent more than dense-graded mixes and still be cost effective on a life-cycle basis.SMA could cost 82 to 94 percent more than dense-graded mixes and still be cost effective on a life-cycle basis. SMA is not typically suited to small quantity productionSMA is not typically suited to small quantity production 65 gyrations recommended as alternative to 50-blow Marshall65 gyrations recommended as alternative to 50-blow Marshall

The complete report is available at: Contact Information for authors: Ray Brown Brian Prowell Don Watson Graham Hurley